Why is he getting close to my friend/s?

Do men try to get closer with someone's friend to make the other person jealous?

I thought this guy liked me but then realized he's getting closer to my friend even though she already has a boyfriend! he knows this & he isn't hitting on her or anything but they talk a lot & him being the odd flirt. In my situation, this guy (who i like) thinks im getting close to this other guy (which we are just friends) & he always asks about us. He flirts with me as well and tries to impress me, he's goofy around me and he asks my friends about me. nothing big as of yet, it's just a little confusing to me that all. Is that a thing? Men luring us in by making you jealous? Or is it just a douche move?